Batch fermentation of black tea by kombucha: A contribution to scale-up

Local domestic Kombucha was used in fermentation of 1.5 g L-1 of black tea (Indian tea, " Vitamin ", Horgos, Serbia and Montenegro), sweetened with approximately 70 g L'1 of sucrose. Inoculation was performed either with 10% or 15% (v/v) of fermentation broth from previous process. The fermentation was conducted in geometrically similar vessels with 0.4 L, 0.8 L, 4 L and 8 L of substrate, at 22?1 ?C for 28 days. The samples were analyzed after 3, 4 5, 6, 7, 10, 14 and 28 days, so that their pH values, content of total acids sucrose, glucose and fructose contents, as well as contents of ethanol and vitamin C were determined. Based on the experiment design, the response surface for the product pH, as a function of time, beverage volume and inoculum concentration, was defined in the form of a second-order polynomial. From the obtained response surface, a formula for scaling-up of the process was derived.